Gonads 1

Question 1

Which cells make up the embryo at 6 weeks

Answer 1

Primordal germ cells
Supporting cells
Steroidogenic cells

Question 2

What do the three aforementioned cells differentiate into?

Answer 2

GC - spermatogonia
Supp - Sertoli
Steroid - Leidig

Question 3

What are the gonads funtcions?

Answer 3

Gametogenesis - spermatogenesis, oogenesis
Steroidogenesis - androgens
oestrogens and progestogens

Question 4

What are gametes derived from? Describe how they stay

Answer 4

Germ cells
- They proliferate, forming 6 million cells
- males stay at this level
BUT
females dips - starts lowering as age, no development post foetus

Question 5

What is atresia?

Answer 5

Degeneration of cells, specifically oogonia

- 7 mil to 400k in piuberty

Question 6

How are gametes formed in males?

Answer 6

Start w germ cells
Then diff to form spermatognia
0 These are DIPLOID

Sperm formation only occurs at puberty, where gonadotrophin release leads to division of spermatogonia

Then, these divide to form PRIMARY SPERMATOCYTES

Undergo meiosis to form SECONDARY sprmatocytes - haploid

THen undergo meiosis again to form SPERMATIDS

THese mature to form SPERMATOZOA

Question 7

How are ova formed?

Answer 7

SAME AS ABOVE
BUT

Germ cell undergoes differentiation to form oogonia
Then these mitose to from Primary oocytes

These then meiose to form secondary oocytes

• As soon as oocytes develop, meiosis stops and oocytes are stuck in Meiosis 1 for 12-50 years
• Arrested cells undergo atresia - decrease numbers

Then, puberty allows formation of ovum via secondary oocytes

Question 8

What causes spermatogenesis, are there any other effects?

Answer 8

Gonadotrophin relase, androgens and testosterone lead to the formation and maturation of testis and semen tubes.

Question 9

Where does spermatogenesis occur?

Answer 9

Sertoli cells in coiled seminiferous tubules, drained into stores in epididymis by vasa efferentia, moved via vas deferens and expelled thru urethra

Question 10

Seminiferous tubule - function? Whats in them?

Answer 10

Along basement membrane is spermatogonia, lined by Sertoli cells, which form a blood-testis barrier

Spermatogonia can traverse this barrier, and this is where they form sperm, before relaease

Question 11

Leydig cells - function?

Answer 11

Enzymes for STEROIDOGENESIS

- testosterone formation

Question 12

Briefly summarise the roles of the Sertoli cells

Answer 12

Form seminiferous tubules

Synthesis androgen and FSH RECEPTORS

Produce INHIBIN when FSH

Form blood-testis barrier

Give nutr

Question 13

Briefly summarise the roles of the Sertoli cells

Answer 13

Outside semi tubue

LH receptors

Respond to LH and principle source of testosterone
- mneeded for spermatogenesis

Question 14

Ovaires

Answer 14

Contains follicles with oocytes that are under different states
- atresia or differentiation

Question 15

What is a Graafian follicle?

Answer 15

Ovum surrounded by Granulosa and Thecal cells that is the largest it’ll be
becomes corpus luteum

Ovaries will have remnants of last corpus luteum

Question 16

What steroid hormones do the gonads make?

Answer 16

Progestogens
Androgens
Oestrogens

Question 17

What is the path for gonad hormone genesis?

Answer 17

Chol
Preg
Prog
17oh prog
androstenedione
17 b hydroxysteroid
testosterone
dht

Then for women,
androstenedione
oestrone

or testosterone
17b oestradiol
BY AROMATASE, activ by FSH

Question 18

Menstrual cycle - how long and what marks the start? What is importnat? What are the two constituents?

Answer 18

28 days 20-35
Begins on first day of menstruation

Ovulation at Day 14

Ovarian cycle
Endometrial cycle

Question 19

Describe the Ovarian Cycle

Answer 19

Follicular phase
- Oestrogen acts on endometrium

(ovulation occurs)

Luteal phase
- Hallmarked by pregesterone
has effects on prolif cylce

Question 20

Describe the Endometrial Cycle

Answer 20

Proliferative
Caused by oestrogen acting on the endometrium - lining thickens
Prepped for stim by progesterone

Secretory

• Stim by progesterone, which also inhibits the proliferative phase
• makes it suitable for implantation

Question 21

Describe the profile of the hormones in cycle

Answer 21

First half is follicular
Second is luteal

FSH and LH surge at Day 14

Oestrogen starts rising and peaks before Day 14 due to the FSH allowing for follicles to proliferate, forming oestrogen

As oestrogen increases, it has negative feedback on gonadotrophins, decreasing their concentration.

Sensitive follicle becomes dominant due to FSH, and produces a lot of oestrogen, which reaches a point that leads to FSH and LH release (also by progesterone blip).

The LH stimulates ovulation

Second half

FOllicle that remains forms corpus luteum, which releases both oestrogen and progesterone.

These hormones negatively feedback the gonadotrophins.

If no fertilisation, the oestrogen and progesterone decrease, allowing FSH and LH to increase for new follicels to develop and new cycle.

Body temp goes up ue to progesterone

Question 22

Ovarian cycle - follicles and diff stages, which hormones needed

Answer 22

Development of follicle to PRE ANTRAL is Gn INDEPENDENT
- atresia if no FSH

After that, need FSH to go to early antral
- Then late, and a dominant one is selected, forms Graafian, ready for ovulation, large fluid space

Egg release then forms corpus luteum, which produces hormones

Question 23

How do follicles produce hormones?

What are the roles of FSH and LH?

Answer 23

Ovum surrounded by granulosa and thecal cells with LH receptors

Thecal cells w LH receptors stimulate steroidogenesis, but no aromatase means that androgens form.
They then move to granulosa cells, where aromatase is present, forming oestrogen. Does this by FSH receptor that activates aromatase.

Question 24

Describe the endometrial cycle

Answer 24

Again, first half is proliferative
-Oestrogen dominant hormone, leading to thickening of endometrium and increases blood supply - coiled

Secretory

• Progesterone dominant
  
  • Stimulates glycogen releases and VD, for blood pooling and tissue engorgment
• Blastocyst arrives for ideal implantation

If no fertilisation, the oestrogen, progesterone decrease due to low FSH and LH and vasoconstriction occurs
- ischemia and necrosis and then shedding
Prostaglandins released to start cramping and release